Representational State Transfer (REST) is a software architectural style for distributed hypermedia systems like the world wide web. The term originated in a 2000 doctoral dissertation about the web written by Roy Fielding, one of the principal authors of the HTTP protocol specification, and has quickly passed into widespread use in the networking community.

While REST and protocol. It is possible to design web service systems in accordance with Fielding's REST architectural style, and it is also possible to design simple XML+HTTP interfaces in accordance with the originally referred to a collection of architectural principles (described below), people now often use the term in a looser sense to describe any simple web-based interface that uses XMLHTTP without the extra abstractions of MEP-based approaches like the web services SOAPRPC style but without actually using SOAP. These two different uses of the term REST cause some confusion in technical discussions, even though RPC is not an example of REST.

Systems that follow Fielding's REST principles are often referred to as RESTful; REST's most zealous advocates call themselves RESTafarians